Lighting systems have been used to illuminate spaces since the discovery of fire. Over the years, technology has brought us the incandescent light, which produces light by heating a metal filament, causing it to radiate heat. Although the incandescent light is capable of illuminating an area, it does so with little efficiency.
The fluorescent lamp was introduced to provide comparable light while using less energy. The fluorescent lamp excites a gas, such as mercury vapor, within a confined volume. The atoms of the excited gas typically produce ultraviolet light as it moves between energy levels. The ultraviolet light is then absorbed by a conversion material, such as a phosphor. The phosphor may shift the wavelength range of the absorbed light, emitting a light with longer wavelengths. This shift may be known to skilled artisans as a Stokes shift. This phosphor-emitted or converted light may be within the visible spectrum, which may be used to illuminate a space.
Seeking additional efficiency, continuing advancements in technology have brought the light emitting semiconductor device, and more specifically, the light emitting diode. Light emitting diodes may emit light when driven by an electrical current. Like fluorescent lights, conversion materials may be applied to a light emitting semiconductor device to alter the wavelength range of the light used to illuminate a space.
Lighting systems that include a conversion material may conveniently allow the conversion of a source light emitted from a light source into light of a different wavelength range. Often, such a conversion may be performed by using a luminescent, fluorescent, or phosphorescent material. The wavelength conversion materials may sometimes be included in the bulk of another material, applied to a lens or optic, or otherwise located in line with the light emitted from light source. In some instances the conversion material may be applied to the light source itself. A number of disclosed inventions exist that describe lighting devices that utilize a conversion material applied to an LED to convert light with a source wavelength range into light with a converted wavelength range.
Additional strategies to reduce power consumption involve controlling a lighting system to illuminate a space only when the illumination is required. Traditionally, toggle switches have been included in lighting circuits to allow a user to directly control the operational state of the light. Additionally, timers maybe be included in the light circuit to turn a light on and off according to a predetermined or dynamic timing schedule. However, switches and timers offer little flexibility unless directly engaged by a user.
Sensors may additionally be included in lighting systems to control operation upon the sensed compliance with a desired event. As an example, sensors may determine the level of light in a space, which may, in turn, cause a lighting system to be turned on upon sensing that a value falls below a threshold value. As an additional example, sensors may detect the presence of movement in a space to control illumination. However, including dedicated sensors may increase the number of parts and complexity required to build the lighting system, thereby increasing its manufacturing cost.
Additionally, each lighting device may operate independent of other lighting devices, requiring sensors included in each lighting device, further increasing production costs. Some proposed solutions have included wireless radio transmitters in the lighting systems, to allow communication between the devices included therein. However, the inclusion of wireless radios further increases the complexity and number of components included in the lighting system.
One proposed solution is described in by international patent application publications WO 2011/016860, WO 2011/008251, WO 2010/098811, and WO 2010/027459, each by Knapp, and that each involve using the light emitting semiconductor device to perform the operations of a photodiode during portions of the duty cycle when the light emitting semiconductor device is not emitting light. The aforementioned Knapp applications additionally recite using the light emitting semiconductor devices to transmit and receive bi-directional communication between devices included in the lighting system. However, the Knapp applications employ data transmission methods that may result in redundant data transmission, decreasing the effective throughput of the system. Additionally, the Knapp applications lack advanced wavelength sensing functionality, limiting the effectiveness of the system disclosed therein.
There exists a need for a wavelength lighting system that can emit an illuminating light and sense an environmental light by altering its operational state between various portions of the duty cycle. There further exists a need for a lighting system that can analyze the sensed environmental light to alter the characteristics of the nodes included in the lighting system. There exists a need for a lighting system that includes a wavelength conversion material to expand the wavelength range of light that may be emitted or detected by a light emitting semiconductor device. Additionally, there exists a need for a lighting system wherein the nodes intercommunicate to increase the effectiveness of the system.